When creating a new subnet, there is no validation that a valid range has been entered, and no default range is automatically selected when empty.

This results in back code being pushed to the DHCP server, which results in the dhcpd server not starting, which results in servers all losing their IP addresses.

(and in the case of a short TTL, a production outage, as just happened to us.)

This is dangerous, DHCP range validation can cause the service to stop so this should be validated in both puppet and foreman UI code.

This occurs in at least Foreman v1.19.1.